Multi-step transmission for vehicle

ABSTRACT

A multi-step transmission for a vehicle may include an input shaft, an output shaft, first to fourth planetary gear devices disposed between the input shaft and the output shaft to transmit rotary force, each of the first to fourth planetary gear devices having three rotary elements, and at least six shifting elements connected to the rotary elements of the planetary gear devices.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent ApplicationNumber 10-2014-0166835 filed Nov. 26, 2014, the entire contents of whichis incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to a multi-step transmission fora vehicle and, more particularly, to a multi-step transmissiontechnology able to realize as many shifting positions as possible usingthe fewest parts possible and the simplest configuration possible.

Description of Related Art

Recent rising oil prices have driven worldwide car manufacturers intounlimited competition to improve fuel efficiency. In addition, greatefforts have been made to reduce the weight and improve the fuelefficiency of engines based on a variety of techniques such asdownsizing.

Among methods that can be sought for transmissions equipped in vehiclesto improve fuel efficiency, there is a method able to improve fuelefficiency by allowing an engine to operate at more efficient operationpoints using a multi-step transmission.

Such a multi-step transmission allows an engine to operate in arelatively low RPM (revolutions per minute) range, thereby furtherimproving the quietness of a vehicle.

However, as the number of shifting positions of a transmissionincreases, the number of internal parts constituting the transmissionalso increases. This may lead to undesirable effects instead, such asthe reduced mountability and transfer efficiency and the increased costand weight of the transmission. Therefore, in order to maximize theeffect of improved fuel efficiency using a multi-step transmission, itis important to devise a transmission structure able to realize maximumefficiency using a relatively small number of parts and a simpleconfiguration.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing amulti-step transmission for a vehicle able to realize at least tenforward shifting positions and one reverse shifting position with arelatively small number of parts and a simple configuration. In variousaspects, an engine operates at optimum operation points, therebymaximizing an improvement in the fuel efficiency of the vehicle and theengine operates more quietly, thereby improving the quietness of thevehicle.

According to various aspects of the present invention, a multi-steptransmission for a vehicle may include an input shaft, an output shaft,first to fourth planetary gear devices disposed between the input shaftand the output shaft to transmit rotary force, each of the first tofourth planetary gear devices having three rotary elements, and at leastsix shifting elements connected to the rotary elements of the planetarygear devices, in which a first rotary element of the first planetarygear device is continuously connected to a third rotary element of thesecond planetary gear device while being fixable by one shifting elementfrom among the at least six shifting elements, a second rotary elementof the first planetary gear device is continuously connected to a secondrotary element of the third planetary gear device and a third rotaryelement of the fourth planetary gear device, and a third rotary elementof the first planetary gear device is fixable by another shiftingelement from among the at least six shifting elements, in which a firstrotary element of the second planetary gear device is selectivelyconnected to a first rotary element of the fourth planetary gear deviceand the second rotary element, a second rotary element of the secondplanetary gear device is continuously connected to the input shaft, thethird rotary element of the second planetary gear device is continuouslyconnected to a third rotary element of the third planetary gear device,in which a first rotary element of the third planetary gear device isselectively connected to the first rotary element and a second rotaryelement of the fourth planetary gear device, and in which the secondrotary element of the fourth planetary gear device is continuouslyconnected to the output shaft.

The first planetary gear device, the second planetary gear device, thethird planetary gear device and the fourth planetary gear may besequentially arranged along an axial direction of the input shaft andthe output shaft.

The first rotary element of the first planetary gear device may befixable to a transmission housing by means of a second clutch from amongthe shifting elements, in which the third rotary element of the firstplanetary gear device may be fixable to the transmission housing bymeans of a third clutch from among the shifting elements, and in whichremaining shifting elements from among the at least six shiftingelements may be configured to constitute selective connection structuresbetween the rotary elements of the planetary gear devices.

A first clutch from among the at least six shifting elements may form aselective connection structure between the first rotary element of thethird planetary gear device and the second rotary element of the fourthplanetary gear device, in which a fourth clutch from among the at leastsix shifting elements may form a selective connection structure betweenthe first rotary element of the second planetary gear device and thesecond rotary element of the third planetary gear device, in which afifth clutch from among the at least six shifting elements may form aselective connection structure between the first rotary element of thesecond planetary gear device and the first rotary element of the fourthplanetary gear device, and in which a sixth clutch from among the atleast six shifting elements may form a selective connection structurebetween the first rotary element of the third planetary gear device andthe first rotary element of the fourth planetary gear device.

According various aspects of the present invention, a multi-steptransmission for a vehicle may include first to fourth planetary geardevices each having the three rotary elements, six shifting elementsconfigured to selectively provide frictional force, and first to eighthrotary shafts connected to the rotary elements of the first to fourthplanetary gear devices, in which the first rotary shaft is an inputshaft directly connected to a second rotary element of the secondplanetary gear device, the second rotary shaft is directly connected toa first rotary element of the first planetary gear device, a thirdrotary element of the second planetary gear device and a third rotaryelement of the third planetary gear device, the third rotary shaft isdirectly connected to a second rotary element of the first planetarygear device, a second rotary element of the third planetary gear deviceand a third rotary element of the fourth planetary gear device, thefourth rotary shaft is directly connected to a third rotary element ofthe first planetary gear device, the fifth rotary shaft is directlyconnected to a first rotary element of the second planetary gear device,the sixth rotary shaft is directly connected to a first rotary elementof the fourth planetary gear device, the seventh rotary shaft isdirectly connected to a first rotary element of the third planetary geardevice, the eighth rotary shaft is an output shaft directly connected toa second rotary element of the fourth planetary gear device, and inwhich the six shifting elements include first to sixth clutches, thefirst clutch is disposed between the seventh rotary shaft and the eighthrotary shaft, the second clutch is disposed between the second rotaryshaft and the transmission housing, the third clutch is disposed betweenthe fourth rotary shaft and the transmission housing, the fourth clutchis disposed between the third rotary shaft and the fifth rotary shaft,the fifth clutch is disposed between the fifth rotary shaft and thesixth rotary shaft, the sixth clutch is disposed between the sixthrotary shaft and the seventh rotary shaft.

According to the present invention as set forth above, the multi-steptransmission for a vehicle can realize at least ten forward shiftingpositions and one reverse shifting position with a relatively smallnumber of parts and a simple configuration. The engine operates atoptimum operation points, thereby maximizing an improvement in the fuelefficiency of the vehicle. The engine operates more quietly, therebyimproving the quietness of the vehicle.

It is understood that the term “vehicle” or “vehicular” or other similarterms as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g., fuel derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example, bothgasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of an exemplarymulti-step transmission for a vehicle according to an exemplaryembodiment of the present invention.

FIG. 2 illustrates an operation mode table of the exemplary multi-steptransmission shown in FIG. 1.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Referring to FIG. 1 and FIG. 2, a multi-step transmission for a vehicleaccording to various embodiments of the present invention includes aninput shaft IN, an output shaft OUT, first to fourth planetary geardevices PG1, PG2, PG3 and PG4 disposed between the input shaft IN andthe output shaft OUT to transmit rotary force, each of the planetarygear devices PG1 to PG4 having three rotary elements, and at least sixshifting elements connected to the rotary elements of the planetary geardevices PG1 to PG4.

The first rotary element S1 of the first planetary gear device PG1 iscontinuously connected to the third rotary element R2 of the secondplanetary gear device PG2 while being fixable by one shifting elementfrom among the at least six shifting elements. The second rotary elementC1 of the first planetary gear device PG1 is continuously connected tothe second rotary element C3 of the third planetary gear device PG3 andthe third rotary element R4 of the fourth planetary gear device PG4. Thethird rotary element R1 of the first planetary gear device PG1 isfixable by another shifting element from among the at least six shiftingelements.

The first rotary element S2 of the second planetary gear device PG2 isselectively connected to the first rotary element S4 of the fourthplanetary gear device PG4 and the second rotary element C3 of the thirdplanetary gear device PG3. The second rotary element C2 of the secondplanetary gear device PG2 is continuously connected to the input shaftIN. The third rotary element R2 of the second planetary gear device PG2is continuously connected to the third rotary element R3 of the thirdplanetary gear device PG3.

The first rotary element S3 of the third planetary gear device PG3 isselectively connected to the first rotary element S4 and the secondrotary element C4 of the fourth planetary gear device PG4. The secondrotary element C4 of the fourth planetary gear device PG4 iscontinuously connected to the output shaft OUT.

The first planetary gear device PG1, the second planetary gear devicePG2, the third planetary gear device PG3 and the fourth planetary geardevice PG4 are sequentially arranged along the axial direction of theinput shaft IN and the output shaft OUT.

The first rotary element S1 of the first planetary gear device PG1 isfixable to a transmission housing CS by device of a second clutch CL2from among the shifting elements. The third rotary element R1 of thefirst planetary gear device PG1 is fixable to the transmission housingCS by device of a third clutch CL3 from among the shifting elements.

Therefore, the second clutch CL2 and the third clutch CL3 function asbrakes, and respectively stop or allow the rotation of the first rotaryelement S1 and the third rotary element R1 of the first planetary geardevice PG1.

The other shifting elements from among the shifting elements areconfigured to constitute selective connection structures between therotary elements of the planetary gear devices.

Specifically, the first clutch CL1 from among the shifting elementsforms a selective connection structure between the first rotary elementS3 of the third planetary gear device PG3 and the second rotary elementC4 of the fourth planetary gear device PG4. A fourth clutch CL4 fromamong the shifting elements forms a selective connection structurebetween the first rotary element S2 of the second planetary gear devicePG2 and the second rotary element C3 of the third planetary gear devicePG3. A fifth clutch CL5 from among the shifting elements forms aselective connection structure between the first rotary element S2 ofthe second planetary gear device PG2 and the first rotary element S4 ofthe fourth planetary gear device PG4. A sixth clutch CL6 from among theshifting elements forms a selective connection structure between thefirst rotary element S3 of the third planetary gear device PG3 and thefirst rotary element S4 of the fourth planetary gear device PG4.

According to various embodiments, the first rotary element S1, thesecond rotary element C1 and the third rotary element R1 of the firstplanetary gear device PG1 are respectively a first sun gear, a firstcarrier and a first ring gear. The first rotary element S2, the secondrotary element C2 and the third rotary element R2 of the secondplanetary gear device PG2 are respectively a second sun gear, a secondcarrier and a second ring gear. The first rotary element S3, the secondrotary element C3 and the third rotary element R3 of the third planetarygear device PG3 are respectively a third sun gear, a third carrier and athird ring gear. The first rotary element S4, the second rotary elementC4 and the third rotary element R4 of the fourth planetary gear devicePG4 are respectively a fourth sun gear, a fourth carrier and a fourthring gear.

The multi-step transmission for a vehicle configured as above may alsobe presented as follows.

Specifically, the multi-step transmission for a vehicle according to anexemplary embodiment of the present invention includes the first tofourth planetary gear devices PG1 to PG4 each having the three rotaryelements, the six shifting elements configured to selectively providefrictional force, and eight rotary shafts connected to the rotaryelements of the first to fourth planetary gear devices.

Here, from among the eight rotary shafts, the first rotary shaft RS1 isthe input shaft IN directly connected to the second rotary element C2 ofthe second planetary gear device PG2. The second rotary shaft RS2 isdirectly connected to the first rotary element S1 of the first planetarygear device PG1, the third rotary element R2 of the second planetarygear device PG2 and the third rotary element R3 of the third planetarygear device PG3. The third rotary shaft RS3 is directly connected to thesecond rotary element C1 of the first planetary gear device PG1, thesecond rotary element C3 of the third planetary gear device PG3 and thethird rotary element R4 of the fourth planetary gear device PG4. Thefourth rotary shaft RS4 is directly connected to the third rotaryelement R1 of the first planetary gear device PG1. The fifth rotaryshaft RS5 is directly connected to the first rotary element S2 of thesecond planetary gear device PG2. The sixth rotary shaft RS6 is directlyconnected to the first rotary element S4 of the fourth planetary geardevice PG4. The seventh rotary shaft RS7 is directly connected to thefirst rotary element S3 of the third planetary gear device PG3. Theeighth rotary shaft RS8 is the output shaft OUT directly connected tothe second rotary element C4 of the fourth planetary gear device PG4.

In addition, from among the six shifting elements, the first clutch CL1is disposed between the seventh rotary shaft RS7 and the eighth rotaryshaft RS8. The second clutch CL2 is disposed between the second rotaryshaft RS2 and the transmission housing CS. The third clutch CL3 isdisposed between the fourth rotary shaft RS4 and the transmissionhousing CS. The fourth clutch CL4 is disposed between the third rotaryshaft RS3 and the fifth rotary shaft RS5. The fifth clutch CL5 isdisposed between the fifth rotary shaft RS5 and the sixth rotary shaftRS6. The sixth clutch CL6 is disposed between the sixth rotary shaft RS6and the seventh rotary shaft RS7.

As set forth above, the multi-step transmission for a vehicle accordingto the present invention including the four simple planetary geardevices and the six shifting elements realizes eleven forward shiftingpositions and one reverse shifting position according to the operationmode table as illustrated in FIG. 2. Since the multi-step transmissioncan be embodied based on a relatively small number of parts and a simpleconfiguration, the multi-step transmission can contribute to theimproved fuel efficiency and quietness of a vehicle, thereby improvingthe salability of the vehicle.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A multi-step transmission for a vehiclecomprising: an input shaft; an output shaft; first to fourth planetarygear devices disposed between the input shaft and the output shaft totransmit rotary force, each of the first to fourth planetary geardevices having three rotary elements; and at least six shifting elementsconnected to the rotary elements of the planetary gear devices, whereina first rotary element of the first planetary gear device iscontinuously connected to a third rotary element of the second planetarygear device while being fixable by one shifting element from among theat least six shifting elements, a second rotary element of the firstplanetary gear device is continuously connected to a second rotaryelement of the third planetary gear device and a third rotary element ofthe fourth planetary gear device, and a third rotary element of thefirst planetary gear device is fixable by another shifting element fromamong the at least six shifting elements, wherein a first rotary elementof the second planetary gear device is selectively connected to a firstrotary element of the fourth planetary gear device and the second rotaryelement of the third planetary gear device, a second rotary element ofthe second planetary gear device is continuously connected to the inputshaft, the third rotary element of the second planetary gear device iscontinuously connected to a third rotary element of the third planetarygear device, wherein a first rotary element of the third planetary geardevice is selectively connected to the first rotary element and a secondrotary element of the fourth planetary gear device, and wherein thesecond rotary element of the fourth planetary gear device iscontinuously connected to the output shaft.
 2. The multi-steptransmission according to claim 1, wherein the first planetary geardevice, the second planetary gear device, the third planetary geardevice and the fourth planetary gear device are sequentially arrangedalong an axial direction of the input shaft and the output shaft.
 3. Themulti-step transmission according to claim 2, wherein the first rotaryelement of the first planetary gear device is fixable to a transmissionhousing by a second clutch from among the shifting elements, wherein thethird rotary element of the first planetary gear device is fixable tothe transmission housing by a third clutch from among the shiftingelements, and wherein remaining shifting elements from among the atleast six shifting elements are configured to constitute selectiveconnection structures between the rotary elements of the planetary geardevices.
 4. The multi-step transmission according to claim 3, wherein afirst clutch from among the at least six shifting elements forms aselective connection structure between the first rotary element of thethird planetary gear device and the second rotary element of the fourthplanetary gear device, wherein a fourth clutch from among the at leastsix shifting elements forms a selective connection structure between thefirst rotary element of the second planetary gear device and the secondrotary element of the third planetary gear device, wherein a fifthclutch from among the at least six shifting elements forms a selectiveconnection structure between the first rotary element of the secondplanetary gear device and the first rotary element of the fourthplanetary gear device, and wherein a sixth clutch from among the atleast six shifting elements forms a selective connection structurebetween the first rotary element of the third planetary gear device andthe first rotary element of the fourth planetary gear device.
 5. Amulti-step transmission for a vehicle comprising: first to fourthplanetary gear devices each having three rotary elements; six shiftingelements selectively providing frictional force to the rotary elements;and first to eighth rotary shafts connected to the rotary elements ofthe first to fourth planetary gear devices, wherein the first rotaryshaft is an input shaft directly connected to a second rotary element ofthe second planetary gear device, the second rotary shaft is directlyconnected to a first rotary element of the first planetary gear device,a third rotary element of the second planetary gear device and a thirdrotary element of the third planetary gear device, the third rotaryshaft is directly connected to a second rotary element of the firstplanetary gear device, a second rotary element of the third planetarygear device and a third rotary element of the fourth planetary geardevice, the fourth rotary shaft is directly connected to a third rotaryelement of the first planetary gear device, the fifth rotary shaft isdirectly connected to a first rotary element of the second planetarygear device, the sixth rotary shaft is directly connected to a firstrotary element of the fourth planetary gear device, the seventh rotaryshaft is directly connected to a first rotary element of the thirdplanetary gear device, and the eighth rotary shaft is an output shaftdirectly connected to a second rotary element of the fourth planetarygear device, and wherein the six shifting elements comprise first tosixth clutches, in which the first clutch is disposed between theseventh rotary shaft and the eighth rotary shaft, the second clutch isdisposed between the second rotary shaft and a transmission housing, thethird clutch is disposed between the fourth rotary shaft and thetransmission housing, the fourth clutch is disposed between the thirdrotary shaft and the fifth rotary shaft, the fifth clutch is disposedbetween the fifth rotary shaft and the sixth rotary shaft, and the sixthclutch is disposed between the sixth rotary shaft and the seventh rotaryshaft.
 6. The multi-step transmission according to claim 5, wherein thefirst planetary gear device, the second planetary gear device, the thirdplanetary gear device and the fourth planetary gear device aresequentially arranged along an axial direction of the input shaft andthe output shaft.
 7. The multi-step transmission according to claim 5,wherein the first clutch is disposed to form a selective connectionbetween the first rotary element of the third planetary gear device andthe second rotary element of the fourth planetary gear device, thefourth clutch is disposed to form a selective connection between thefirst rotary element of the second planetary gear device and the secondrotary element of the third planetary gear device, the fifth clutch isdisposed to form a selective connection between the first rotary elementof the second planetary gear device and the first rotary element of thefourth planetary gear device, and the sixth clutch is disposed to form aselective connection between the first rotary element of the thirdplanetary gear device and the first rotary element of the fourthplanetary gear device.